The present disclosure relates to semiconductor substrate structures having bumps and semiconductor devices having bumps.
In a technical field of packaging semiconductor devices, bump electrodes have been formed for chip-size packages, chip-scale packages, flip-chips, and the like. The bump electrodes have bumps such as electrode pads, metal balls, and the like. In the surroundings of the bump electrode, a passivation film, a protective film for protecting a top surface, and the like are generally formed. For formation of the bump electrodes, a printing method, a plating method, a bump material mounting method, and the like have been used.
In the printing method, after a printing mask is positioned, a printing paste including a bump material paste and a flux is supplied on a wafer through the printing mask. Then, bumps are formed by performing a reflow process. In processing fine patterns, the printing method has a problem of causing variation of diameters of bumps formed after the reflow process since the printing paste is less likely to be released from the printing mask in processing fine patterns.
In the plating method, bumps are formed on an electrode pad by electrolytic plating or electroless plating. When the plating method is processed, it is necessary to control a current used for plating depending on the number of electrodes, thereby making the current control complicated. Therefore, the method has a problem with the shape precision of the bumps.
The bump material mounting method has been used for ball grid arrays (BGAs) and the like, and it is a method of, after gripping bump materials onto a suction head, mounting (transferring) the gripped bump materials all at once on an electrode pad. In the bump material mounting method, when each of the bump materials is small, it becomes difficult to grip the bump materials all at once onto the head. Thus, such a one-time transfer is said to have an upper limit of several thousands of materials. As a method to increase the scale of the one-time transfer, a method by using a mask for mounting has been considered (for example, see Japanese Patent Publication No. 2000-332151). This is a method of mounting bump materials which are to be used for forming bumps all at once on an electrode pad through a mask for mounting that has an opening whose diameter is equal to or larger than that of the bump material. The method, by using a mask having approximately the same thickness as the bump material, and having an opening into which the bump material drops, supplies and disposes the bump materials which are to be used for forming the bumps. Therefore, it is possible to precisely and efficiently supply and dispose the bump materials in necessary positions.